Some fuels burned by oil lamps produce relatively large amounts of smoke, but are still in use because they have other beneficial properties. For example, citronella oil produces smoke but is useful for repelling insects, such as mosquitoes.
Air drafts around the flame tend to increase the amount of smoke produced, so some existing lamps provide a shield around the flame to protect from air drafts. However, shielding the flame from air drafts can result in an inadequate air supply to the flame. This inadequate air supply results in incomplete combustion, which has several side effects. One side effect is an increase in the amount of smoke produced. Another side effect is a flame that is non-uniform in color and luminosity, with a bright area at the top of the flame and a dark area in the bottom center.
A well-known technique to control the height of a flame involves increasing or decreasing the amount of wick exposed to the fuel. For example, an adjusting knob or screws can be used to raise or lower the wick. However, the adjusting knob increases the cost of the lamp, and is often hard to clean. A need therefore exists to address these and other shortcomings in the prior art.